This invention relates to noise generators. In particular, this invention relates to underwater noise generators actuated from a remote location by acoustic signals or magneto-inductive signals propagated at extremely low to very low frequencies to produce bubbles that create acoustic noise that may conceal movements or deceive listeners.
Currently, electromechanical pingers, sacrificial vehicles, and remotely controlled vehicles are used to create noise in a given area. Some systems use explosive charges to create underwater acoustic noise. These devices for producing noise, however, are difficult to inconspicuously emplace at one time and reliably actuate later by remote means when the tactical situation is more favorable.
Previously, acoustic command signals have been used to control a variety of instrumentation and ordnance packages. However, acoustic command signals have limited applications since sound cannot effectively be communicated through the air to receivers in the water. In addition, reliable communication with acoustic devices is affected by sediment, microorganisms, algae, changes in salinity, thermoclines, and multi paths in the water. Acoustic devices may also be unreliable at detecting acoustic command signals in the water in the presence of ambient noise that may come from ships, mammals, munitions, landing craft, sonar, and crashing surf. Acoustic devices are known to be incapable of reliable performance in the littoral regions associated with amphibious assault, particularly in the surf zone and noisy harbors.
A further limitation in the use of acoustic signals is that they are undesirable from a stealth perspective. If an acoustically responsive package is emplaced and an attempt is made to communicate with it using sonar from a friendly submarine, for example, the submarine's position may be given away and triangulated upon by others using passive acoustic detection in the area.
Thus, in accordance with this inventive concept, a need has been recognized in the state of the art for an underwater noise generator creating noise from bubbles in response to remotely originating acoustic or magneto-inductive signals.